The present invention relates to decoding of multiple objects from an encoded multi-object signal based on an available multichannel downmix and additional control data.
Recent development in audio facilitates the recreation of a multi-channel representation of an audio signal based on a stereo (or mono) signal and corresponding control data. These parametric surround coding methods usually comprise a parameterisation. A parametric multi-channel audio decoder, (e.g. the MPEG Surround decoder defined in ISO/IEC 23003-1[1], [2]), reconstructs M channels based on K transmitted channels, where M>K, by use of the additional control data. The control data consists of a parameterisation of the multi-channel signal based on IID (Inter channel Intensity Difference) and ICC (Inter Channel Coherence). These parameters are normally extracted in the encoding stage and describe power ratios and correlation between channel pairs used in the up-mix process. Using such a coding scheme allows for coding at a significant lower data rate than transmitting the all M channels, making the coding very efficient while at the same time ensuring compatibility with both K channel devices and M channel devices.
A much related coding system is the corresponding audio object coder [3], [4] where several audio objects are downmixed at the encoder and later on upmixed guided by control data. The process of upmixing can be also seen as a separation of the objects that are mixed in the downmix. The resulting upmixed signal can be rendered into one or more playback channels. More precisely, [3,4] presents a method to synthesize audio channels from a downmix (referred to as sum signal), statistical information about the source objects, and data that describes the desired output format. In case several downmix signals are used, these downmix signals consist of different subsets of the objects, and the upmixing is performed for each downmix channel individually.
In the new method we introduce a method were the upmix is done jointly for all the downmix channels. Object coding methods have prior to the present invention not presented a solution for jointly decoding a downmix with more than one channel.